<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .shan{
            width: 0px;
            height: 0px;
            border: 50px solid #000;
            border-radius: 50%;
            /* transform: rotate(45deg); */
            border-bottom-color: transparent;
            border-right-color: transparent;
            border-left-color: transparent;
        }
    </style>
</head>
<body>
    <div class="shan"></div>
    <!-- 实现一个扇形 -->
</body>
</html>